Abstract Detail

Morphophisiological adaptations associated with terrestial and epiphytic habits in Orchidaceae.

Various structural modifications and physiological adaptations are related with the expression and emergence of epiphytism in the Orchidaceae. Orchid leaves, whose main function involves an obligatory loss of water, usually possess special modifications in their anatomy, physiology and morphology to reduce the loss of water. To contribute toward the understanding of the adaptive capabilities of orchids, we analyzed the variation of foliar characteristics, such leaf and cuticle thickness, sclerophylly, succulence, water retention after 24 hours, specific leaf area and leaf dry mater content—in orchid species capable of developing as terrestrial plants as well as epiphytes in a humid montane forest. The study was developed in the subandean forests (1750–2500 m of alt) of the Municipio of Pueblo Rico, Risaralda (Colombia), and included five species of orchids: Elleanthus aureus (P. & E.) Rchb. f., Elleanthus oliganthus (P. & E.) Rchb. f., Elleanthus purpureus (Rchb. f.) Rchb. f., Pleurothallis cordifolia Rchb. f. & Wagener and Pleurothallis sp. Three of these species (Elleanthus oliganthus, E. purpureus and Pleurothallis sp.), presented significant differences in their foliar characteristics between its terrestrial and epiphyte representatives, demonstrating a capacity to change their growth strategy. When plants exhibit this flexibility to develop in one way versus another, depending on the circumstances they encounter, they are behaving adaptively. However, this plasticity seems not to be essential for establishment, since the other species studied can develop as epiphyte and terrestrial plants without varying their foliar characteristics and growth strategies.